Production of metallic alloys



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WILLIAM BOWMAN nnnmNr-mnor LONDON, ENGLAND, ASSIGNOR- TO THE EMPIRE(ALLOY) STEEL CORPORATION, LIMITED, OF LONDON, ENGLAND, A BRITISH COR-POBATION.

PRODUCTION OF METALLIC ALLOYS.

,9 Specification of Letters Patent.

. Ho Drawing.

in or relating to the production of metallic alloys, particularlyferro-alloys, such for.

example as ferro-chrome, and the object is to render the production moreeconomical.

Various economical methods are known for the production of ferro-alloyscontaining a higher percentage of carbon, such as 1% to 8% of carbon.These ferro-alloys .with a higher percentage of carbon are manufactured,for example, in blast furnaces, electric furnaces, and in other ways, ata cost which enables them to be sold at a price very much below that offerrO-alloys with a low carbon content. The object of this invention isto provide means for the 'economical production of ferro-alloys having alow percentage of carbon (say 0.15%

or less of carbon).

According to this invention the process for the economical production offerro-al-- loys containing a low percentage of carbon consists in takinga high-carbon ferro-alloy, remelting the same, 1f necessary, for examplein a cupola furnace, running the molten metal directly into 'a converterof the v blast-or Bessemer-type, and blowing atmospheric air through themolten mass until the proportion of carbon has been resupplied to thecupola furnace or to theduced to any desired percentage, after which thealloy is used or treated in any usual way.

Where the ferro-alloy dealt with in this -manner requires, for itsifusion, a temperature higher than that obtainable in theordinary-coke-fired cupola furnace, the air Bessemer or like converter,or to both, may bepre-heated either by utilizing the waste heat of thesaidcupola furnace or the converter, or in any other suitable manner.

According to one feature of this inven tion, the process for theproduction of forme e a lers u nw when content prisessubmitting crudeferro-chrome, obtained, for example, by reduction'of chromite in anelectrical furnace, to decarburizafor the production of electric steels.

tion in a Bessemer or like converter. Preferably, the crude ferro-chromeis mixed with a molten mild basicsteel prior to treatment in theconverter. According to this invention also. the molten. alloy producedin the converter may be treated, either before or after tapping, with athermo-reduction mixture containing a pure chromium compound, morder tocompensate for loss during the process or to provide the desiredercentage of chromium in the final alloy. n the preferred method ofoperation, the thermo-reduction mixture is added to the molten alloy ncompacted form, for example, in a canister or as a briquet. Oxids ofchromium and iron, either alone or in combination, may be used to assistthe oxidation of the excess of carbon in the converter.

The crude ferro-chrome may be prepared by the reduction of chromite inan electric furnace, the charge consisting of chromite and anthracitecoal, or coke, in the calculated respective proportions. Steelscrap orlike material may form part of the charge,

as desired. Anyof the usual-types of furnace may be employed, such asthe Heroult, or Girod, or other type of furnace emplo ad e ferro-chromeobtained is usually fairly rich Patented Aug. 9, 1921. Application filedAugust 19, 1920. Serial No. 404,550.

in carbon, althou hit is possible under cer- A tain conditions, orexample, by prolonged heating of the impure alloy in an arc furs nacewith special slags as chromite, lime and fiuor-spar, to produce an alloycontainmg less than 2 per cent. of carbon. The further decarburizationis effected in the Bessemer converter as in the manner for the treatmentof molten pig iron, the progress of the oxidation being judged, as inthe usual Bessemer operation, by the flame colors and other phenomenafamiliar to those skilled in the art.

The converter may be a hub converter capable of holding a chargeof a ut.5 tons, and it may be lined with an acidic or'a basic lining, or aneutral refractory, such as chromite, may be used. As stated, oxids ofchromium and iron may be employed to assist the oxidation process.

By treatment in the converter, the carbon content of the ferro-chromemay be reduced to about 1 per cent, or the oxidation may be continueduntil a very low carbon content is obtained. As the operation proceedsmore of the alloying metals are oxidized and ass into the slag, butslags rich in oxi of chromium may be used as part of the charge in theelectric furnace in the process for the production of the crudeferro-chrome.

The admixture of the crude ferro-chrome with mild basic steel, prepared,for example,

in' the same or in an adjacent converter, fa-

' metal or metals to, form the free metal or metals, the process ofreduction being ac-v companied by the evolution of heat. Aluminium inthe powdered or granulated form is perhaps the best known of the.reducing agents, in this reaction, but other wellknown reagents arecalcium silicid, calcium, magnesium, calcium carbid, silicon, and so on,and these and other such suitable reagents may be used either separatelyor in any combination. The chromium .in the thermo-reduction mixture maybe in the form of chromite, or of a ure compound of chromium,.such aschromium oxid, or of a mixture of these, in association with one or moreof the known thermo-reducing agents such as those mentioned. The amountof such a mixture-added is such as to enrich the molten alloy by theamount of metallic chromium necessary to give the final ferrochromealloy with the desired chromium content, and to compensate for lossesduring the decarburization process, without, at the same time increasingthe content in carbon.' The addition of the reduction mixture may bemade in any suitable way, but it has been found preferable to add themixture in the form of a block or similar compacted mass, so that thereaction takes place under the surface of the molten metal.- By thismeans a ferro-chrome alloy of more uniform standard may be produced andadvantage is taken of-the heat of the molten mass, for ex- I ample themolten steel employed to mix with the crude ferro-chrome, to bring thecharge for the converter tothe necessary temperature more quickly.Further, the additionby raising and -bymaintaining the" heat of themolten mass facilitates the duction of a homogeneous alloy.

It is to be understood that the invention is not restricted to crudeferro-chromes propro- ' duced by any one method. For example,

instead of using an electric furnace forthe' preparation of the crudeferrochrome, a I

ferro-chrome alloy which has been prepared in the blast -furnace may beemployed. This is not so rich in chromium, the percentage mannermanufacture of the ferro-chrome alloy of low carbon content, which.comprises submitting .a molten ferro-chrome alloy of high carbon contentto. the action of an oxidizing blast.

2. The herein described process for the manufacture of a ferro-chromealloy of low carbon content, whi'ch.comprises melting a ferro-chrome.alloy of higher carbon content,

running the molten alloy into a converter,.

and submittin the molten alloy to the action of an oxi 'zing blast.

3. The herein described process for the manufacture of a ferro-chromealloy of low carbon content, which comprises melting a ferro-chromealloy of higher carbon content with mild basic steel, running the moltenmass into a converter, and submitting the molten material to the actionof an oxidizing blast. 1

l. The herein described process for the manufacture of a ferro-chromealloy of low carbon content,-which comprises submitting a moltenferro-ch-rome alloy of higher'carbon content to the action of anoxidizing blast, and adjusting the proportion of chromium in thedecarbonized alloy bytreatment of the latter while molten with athermo-reduction mixture containing chromium oxid.

5. The herein described process for the manufactureof ferro-chrome alloyof low carbon content, which comprises melting a ferro-chrome alloy ofhigher carbon content with mild basic steel, running the molten massinto a converter, submittin the molten material to the action of an oxiizing blast, and adjusting the proportion of chromium in thedecarburized alloy by treatment of the latter in the converter with athermo-reduction mixture containing chromium oxid.

'6. A process for the economical production of ferr c-chrome .of lowcarbon content, which consists in preparing ferro-chrome of high carboncontent by a reduction of chromium bearing ore, running the molten alloyinto a Bessemer or like converter, and subjecting-it to an oxidizingblast or blowing operation to decarbur-ize the alloy to the extentdesired.

. lln testimony whereofll afix my signature.

Wlhtlllll] BQWUAU BM LANTTEJE.

